Field
This application pertains to vertical axis wind turbines, specifically those with rotors having an unbroken perimeter formed by three reflex camber surfaces, enveloping a rotor core.
Prior Art
Three types of vertical axis wind turbines are well known, each of which with many variations:
1. Drag powered turbines such as anemometers which have a rotor made up of cupped or curved shaped elements, mounted around a central shaft. The cupped or curved elements create more drag from the wind from one direction than from the opposite direction. The difference in drag on one half of the rotor from the other half of the rotor causes the rotor to spin in the wind.2. Darrieus type turbines which use airfoil shaped blades, or wings, are typically the most efficient of the vertical axis wind turbines.3. Savonius type turbines have curved blades that bypass each other near the center axis. Savonius wind turbines are not generally thought of as airfoil turbines. However, with efficiencies improving as development continues, it is apparent that they are capable of being more than just drag powered turbines. The Savonius rotor assembly of U.S. Pat. No. 5,494,407 shows improved performance over earlier models although problems with supporting large thin blades still remain a challenge. Pulsating power requires heavy bracing. Large top and bottom plates are required for blade attachment and add unwanted drag.
When the Savonius rotor of U.S. Pat. No. 5,494,407 is viewed as a single airfoil it can be described as a vented reflex airfoil with camber reversing on each side of the axis.